From: Qu Wenruo <wqu@suse.com>
Date: Fri, 26 Sep 2025 04:50:11 +0000 (+0930)
Subject: btrfs: only set the device specific options after devices are opened
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=b7fdfd29a136a17c5c8ad9e9bbf89c48919c3d19;p=users%2Fhch%2Fmisc.git

btrfs: only set the device specific options after devices are opened

[BUG]
With v6.17-rc kernels, btrfs will always set 'ssd' mount option even if
the block device is not a rotating one:

  # cat /sys/block/sdd/queue/rotational
  1
  # cat /etc/fstab:
  LABEL=DATA2     /data2  btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/,nofail,nosuid,nodev      0 0

  # mount
  [...]
  /dev/sdd on /data2 type btrfs (rw,nosuid,nodev,relatime,ssd,space_cache=v2,subvolid=5,subvol=/)

[CAUSE]
The 'ssd' mount option is set by set_device_specific_options(), and it
expects that if there is any rotating device in the btrfs, it will set
fs_devices::rotating.

However after commit bddf57a70781 ("btrfs: delay btrfs_open_devices()
until super block is created"), the device opening is delayed until the
super block is created.

But the timing of set_device_specific_options() is still left as is,
this makes the function be called without any device opened.

Since no device is opened, thus fs_devices::rotating will never be set,
making btrfs incorrectly set 'ssd' mount option.

[FIX]
Only call set_device_specific_options() after btrfs_open_devices().

Also only call set_device_specific_options() after a new mount, if we're
mounting a mounted btrfs, there is no need to set the device specific
mount options again.

Reported-by: HAN Yuwei <hrx@bupt.moe>
Link: https://lore.kernel.org/linux-btrfs/C8FF75669DFFC3C5+5f93bf8a-80a0-48a6-81bf-4ec890abc99a@bupt.moe/
Fixes: bddf57a70781 ("btrfs: delay btrfs_open_devices() until super block is created")
CC: stable@vger.kernel.org # 6.17
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index d6e496436539..aadc02374b2a 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1900,8 +1900,6 @@ static int btrfs_get_tree_super(struct fs_context *fc)
 		return PTR_ERR(sb);
 	}
 
-	set_device_specific_options(fs_info);
-
 	if (sb->s_root) {
 		/*
 		 * Not the first mount of the fs thus got an existing super block.
@@ -1946,6 +1944,7 @@ static int btrfs_get_tree_super(struct fs_context *fc)
 			deactivate_locked_super(sb);
 			return -EACCES;
 		}
+		set_device_specific_options(fs_info);
 		bdev = fs_devices->latest_dev->bdev;
 		snprintf(sb->s_id, sizeof(sb->s_id), "%pg", bdev);
 		shrinker_debugfs_rename(sb->s_shrink, "sb-btrfs:%s", sb->s_id);